Redox switching and oxygen evolution at oxidized metal and metal oxide electrodes: iron in base

Lyons, Michael E. G.; Doyle, Richard L.; Brandon, Michael

doi:10.1039/c1cp22470k

Cited by 101 publications

(117 citation statements)

References 144 publications

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“…The rate of oxide growth is known to decrease with increasing number of growth cycles. Lyons and coworkers 11 have noted that this decrease can be attributed to the increasing inhibition of water and hydroxide ion transfer to the inner region of the oxide layer with increasing hydrous oxide thickness and that this effect becomes more marked with increasing base concentration. Evidently, increased hydroxide ion activity suppresses hydroxide dissociation and/or favours adsorption of this species thereby inhibiting nucleation and growth of the microdisperse hydrous layer.…”

Section: Steady-state Polarisationmentioning

confidence: 99%

“…1. The surface redox chemistry and the factors affecting the growth of hydrous iron oxides in base have been discussed in detail by Lyons and coworkers 11,30 and thus we offer only a brief outline here. It is clear from Fig.…”

Section: Preparation and Voltammetry Of Hydrous Iron Oxidesmentioning

confidence: 99%

“…It has been noted that dispersed hydrated oxide materials exhibit good electrocatalytic potentiality due to their skeletal nature as the latter structural feature permits a major increase in the number of oxyions participating in the electrode reaction. 11,30 Indeed, with microdispersed species the boundary between the solid and aqueous phase may be nebulous as the two phases virtually intermingle. This will be an important consideration when a model for the OER is developed.…”

Section: Preparation and Voltammetry Of Hydrous Iron Oxidesmentioning

confidence: 99%

“…Hence, when the electrochemical oxo generation step eqn (11) is rate limiting at high overpotentials the flux expression presented in eqn (28) predicts that a reaction order of unity with respect to hydroxide ion activity and a Tafel slope of ca. 120 mV dec À1 at 298 K (b = 2.303(2RT/F)) will be observed, Scheme 1 Mechanism for the OER involving octahedrally coordinated Fe oxyhydroxide surfaquo group.…”

Section: This Journal Is C the Owner Societies 2013mentioning

confidence: 99%

“…Although they possess inferior electrocatalytic activity for the OER, their relatively low cost and long term corrosion resistance in alkaline solution makes them attractive OER anode materials. [7][8][9][10][11][12] At present, a significant body of research exists on the application of non-noble transition metal oxides as OER anodes. Amongst the most promising materials are various intermetallic alloys, 13 electrodeposited nickel, 14 cobalt 15 and manganese oxides, 16 spinels including nickelites, 17 cobaltites 18 and ferrites, 19 perovskites, 20 and hematite photoanodes.…”

Section: Introductionmentioning

confidence: 99%

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An electrochemical impedance study of the oxygen evolution reaction at hydrous iron oxide in base

Doyle

Lyons

2013

Phys. Chem. Chem. Phys.

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233

209

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The oxygen evolution reaction at multi-cycled iron oxy-hydroxide films in aqueous alkaline solution is discussed. Steady-state Tafel plot analysis and electrochemical impedance spectroscopy have been used to elucidate the kinetics and mechanism of oxygen evolution. Tafel slopes of ca. 60 mV dec À1 and 40 mV dec À1 are found at low overpotentials depending on the oxide growth conditions, with an apparent Tafel slope of ca. 120 mV dec À1 at high overpotentials. Reaction orders of ca. 0.5 and 1.0 are observed at low and high overpotentials, again depending on the oxide growth conditions. A mechanistic scheme involving the active participation of octahedrally coordinated anionic iron oxyhydroxide surfaquo complexes, which form the porous hydrous layer, is proposed. The latter structure contains considerable quantities of water molecules which facilitate hydroxide ion discharge at the metal site during active oxygen evolution. This work brings together current research in heterogeneous electrocatalysis and homogeneous molecular catalysis for water oxidation.

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Section: Steady-state Polarisationmentioning

confidence: 99%

Section: Preparation and Voltammetry Of Hydrous Iron Oxidesmentioning

confidence: 99%

Section: Preparation and Voltammetry Of Hydrous Iron Oxidesmentioning

confidence: 99%

Section: This Journal Is C the Owner Societies 2013mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An electrochemical impedance study of the oxygen evolution reaction at hydrous iron oxide in base

Doyle

Lyons

2013

Phys. Chem. Chem. Phys.

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233

209

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Status and Prospects of Alkaline Electrolysis

Zhang

Zeng

2016

Hydrogen Science and Engineering : Materials, Processes, Systems and Technology

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Bi‐Functional Iron‐Only Electrodes for Efficient Water Splitting with Enhanced Stability through In Situ Electrochemical Regeneration

Martindale

Reisner

2015

Advanced Energy Materials

152

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are the indirect conversion of solar into chemical energy using a photovoltaic (PV)-electrolyzer [ 9,10 ] system and its direct conversion with a photoelectrochemical (PEC) cell. [11][12][13] The International Energy Agency identifi ed a key obstacle to the widespread implementation of water splitting technologies to be the development of cheap and active materials to catalyze both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which operate under identical and mild conditions with high efficiency and stability. [ 14 ] The most active catalysts of the HER and OER contain precious metals: Pt and RuO 2 /IrO 2 , respectively, [15][16][17][18] but there is no real possibility to scale up these materials for global demand due to their scarcity. A sustainable and global process will require the use of inexpensive, widely abundant and nontoxic materials. Figure S1 (Supporting Information) shows the recent cost of transition metal resources and their relative crustal abundance. Rare, high cost elements are suitable for use in luxury items such as catalytic converters in automobiles. Even medium cost-abundance catalysts such as the much investigated HER catalysts, Ni-Mo alloys, [ 19,20 ] as well as Ni 2 P, [ 21 ] CoP, [ 22 ] and MoS 2 , [23][24][25][26] and the OER catalysts, cobaltphosphate (CoP i ), [ 27 ] nickel-borate (NiB i ), 25 and (mixed) metal oxide-hydroxides [29][30][31][32] can still suffer from scalability issues. For example, cobalt constitutes the largest cost in most Li-ion rechargeable batteries (LiCoO 2 ), which has contributed to significant research into its replacement with iron (LiFePO 4 ) and manganese (LiMnO 2 ) analogs. [ 33 ] Approaches to overcome the use of more expensive metals in catalysis include the use of ultra-low concentrations of the active catalyst embedded in a lower-cost matrix [ 34 ] or in this case the identifi cation of active species which contain only Earth-abundant elements. [ 30 ] Only three transition metals (titanium, manganese, and iron) are truly abundant in Earth's crust (the primary source of metal ores) and within this group, iron is by far the most plentiful. Hence iron is arguably the most attractive element on which to base sustainable catalysts, due to its effectively inexhaustible supply, low toxicity, and negligible environmental impact. Despite this, iron-based catalysts have been relatively underreported and underused, probably due to their notoriety for corrosion.Iron-based electrodes for either the HER or the OER have been reported, [35][36][37][38][39][40] but bi-functionally active iron-only materials in water splitting are unknown. For example, FeP is described as a promising high activity noble-metal-free material Scalable and robust electrocatalysts are required for the implementation of water splitting technologies as a globally applicable means of producing affordable renewable hydrogen. It is demonstrated that iron-only electrode materials prove to be active for catalyzing both proton reduction and water oxidation in alkali...

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Redox switching and oxygen evolution at oxidized metal and metal oxide electrodes: iron in base

Cited by 101 publications

References 144 publications

An electrochemical impedance study of the oxygen evolution reaction at hydrous iron oxide in base

An electrochemical impedance study of the oxygen evolution reaction at hydrous iron oxide in base

Status and Prospects of Alkaline Electrolysis

Bi‐Functional Iron‐Only Electrodes for Efficient Water Splitting with Enhanced Stability through In Situ Electrochemical Regeneration

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